bn/bn_exp.c: prefer MULX/AD*X over AVX2.

openssl · Oct 9, 2013 · 37de2b5 · 37de2b5
1 parent 2d75273
commit 37de2b5
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
@@ -691,7 +691,8 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
 	 * RSAZ exponentiation. For further information see
 	 * crypto/bn/rsaz_exp.c and accompanying assembly modules.
 	 */
-	if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024)
+	if (((OPENSSL_ia32cap_P[2]&0x80100) != 0x80100) /* check for MULX/AD*X */
+	    && (16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024)
 	    && rsaz_avx2_eligible())
 	    	{
 		if (NULL == bn_wexpand(rr, 16)) goto err;